The appearance of atherosclerotic lesions at specific locations in the arterial tree has led many investigators to study the relevance of hemodynamic factors in atherogenesis. The purpose of this study is to investigate the patterns of flow in models of arterial geometries and seek correlations between these flow patterns and the development of atherosclerotic plaques. In previous studies, quantitative measurements of the wall shear stress were made in model arteries by an electrochemical technique. However, the work provided no information about the direction of the shearing forces, and little idea about the nature of the flow patterns. In this study we will use various methods of flow visualization such as dye injection, hydrogen bubbles, and neutrally buoyant microsphere tracers to study the flow patterns in arterial models as a function of various flow parameters such as Reynolds number, branch flow ratios, and pulsatility. Both still photography and high-speed cinematography will record the flow phenomena. The work is in preliminary development stages, and various flow visualization techniques are being evaluated and refined. The electrochemical technique will be used to measure average mass transfer coefficients to the artery wall under conditions of steady and pulsatile flow.